Gear-wheel



E. H. WINGQVIST.

v GEAR WHEEL. APPLICATION FILED JULY 8, I919.

1,390,414. Patentedsept- 13; 1921.

iERIK i-rcrnmaan wrlvsovrs'r, or eo'rrnn aone, swEDE'N, AssIeNoR'To AKTIEBoLAe-Er 'SVENSKAKUGG-HJULSFABBIKEN, or GOTTENBQRG, SWEDEN, A CORPORATION or SWE EN.-

The present invention relates ,to gearwheels, cylindrical as well asy'conical, and

has for its principal purposelto provide a shape of gear tooth which is considerably more capable of resistance to bending stresses than the shapes of teeth. heretofore used;,

In. cylindrical gear-wheels astheretofore 1 used the height of the tooth is constant along the whole breadth of the tooth, whereas conical gear-wheels the height of the tooth is generally greatest at the base end and decreases toward thetop end ofthewheel. In the first instance the bending..moment is constant along the whole breadth of the tooth, whereas in the. second instance the bending moment isgreatest at the base end oflthe wheel. If. the. tooth. is broken,.due

'for instance ito an. overload, the breakage will obviously occur at the point where the bending moment is greatest, and the moment of resistance is smallest, that is to say one end of; the tooth infcylindrical gearwheel s, and at the smaller end" of the tooth in conicalgearewheels;

The present invention has for its purpose to decrease the risk of the teeth breaking and it consists principally in that the top surfaces of the teeth are convex in the longitudinal direction of :the tooth, the bending.

moment thus becoming decreased at the points which are liable to break. The convex surface should preferably be so located that the height of the tooth is greatest at a point intermediate the ends of the tooth.

The invention is illustrated in the accompanying drawing. Figure 1 shows a portion of a cylindrical gear-wheel having the well known shape of the teeth. Fig. 2 shows a portion of a cylindrical gear-wheel with the teeth shaped according to the present invention. Figs. 3 and 4 show two modified shapes of teeth according to the invention.

In the figures, the dotted line m extending GEAR-WHEEL;

Specification of Letters Patent Patented Sept. 1-3, 1921.

1919. seri ai 'no. 309,303.

through the length ofthe teeth isthe pitch line, which inthe case ofacylindrical gear if a longitudinal section of the pitch cylin- According to Fig. l the height ,of the tooth .1 is constant along theentire breadth of the tooth, and'a break, if any, will occur on thedottedand dashed line 2. The dotted ofithe' tooth l is convex in the longitudinal.

direction of the tooth. The curve of the-top surface l'is symmetrical with the pitch line 1 m, lso that" the middle of the tooth is the V The embodimentillustratedin Fig. 3 differsfrom the embodiment according to Fig. 2 principally by the bottom surface 5 of'the space between 'teeth being concave in the longitudinal 7 direction, by which means the bending moment at: the nds of the tooth is still 7 more decreased, provided that the height of the toothis unchanged atthe cen- 1 ter of the tooth. "By making the bottom surface of the space between teeth concave in the longitudinal direction the essential ad- .vantage is also attained that the space between teeth may be formed according to the rolling off principle by means of two cutters having plane cutting surfaces and placed at an angle to one another, which-cutters, by'

being suitably adjusted relatively to one another andto the wheel blank, may be used for producing'gearewheels of any diameter i and any pitch,'which result can not be aty tained, as is well known, by means of the ordinary profile cutters; .The advantag is also attained that intwo meshing wheels the top surface 3 and the bottomsurface 5 are caused to come nearer toone another than for instance in the construction according to Fig. 2. In view of the fact that by shaping the space between teeth by means of two cutters arranged in the manner above described, the bottom surface 5 of the space between teeth becomes elliptically shaped in the longitudinal direction, it is suitable also to make the top surface 4 of such shape.

The embodiment according to Fig. 4 differs from the embodiment according to Fig.

3 only by the height at the ends of the tooth being practically ml, or at any rate very small as compared with the height at the center of the tooth l.

As stated above, the invention is not limited to cylindrical gear-wheels, but it is also directly applicable to conical gear-wheels. It will also be understood that the invention is applicable whether the gear-wheel has helical or straight teeth.

Finally, it is to be observed that the top surface of the tooth may be ridge-shaped or angle-shaped in the longitudinal direction instead of convex, the point being located at or near the center of the tooth;

I claim:

1. A toothed gear-wheel having teeth the top surfaces of which are convex in the longitudinal direction of the tooth in such manner that the height of the tooth, and thus the bending moment, is decreased toward the ends of the tooth, said teeth being shaped in such manner that when meshing with the teeth of another gear wheel, they touch the latter teeth along the whole length of the tooth.

2. A toothed gear-wheel having teeth the top surfaces of which are shaped elliptically convex in the longitudinal direction of the tooth in such manner that the height of-the tooth, andthus the bending moment, is decreased toward the ends of the tooth, said teeth being shaped in such manner that, when meshing with the teeth of another gear wheel, they touch the latter teeth along 7 the whole length of the tooth.

3. A gear wheel according to claim 1, in which the bottom surfaces of the spaces between the teeth are concave'in the longitudinal directionof the teeth.

4:. A gear wheel according to claim 2, in

top surfaces of which are convex in the 1ongitudinal direction of the tooth -andhaving their greatest height at a point intermediate the ends of the tooth, said teeth being shaped in such manner that, when meshing with the teeth of another gear wheel, they touch the latter teeth along the whole length of the tooth.

6. A toothed gear-wheel having teeth the top surfaces of which arerconvex in the 1ongitudinal direction of the tooth and having their greatest height approximately at the center of the tooth, said teeth being shaped in such manner that, when meshing with the 5. A toothed gear-wheel having teeth the teeth of another gear wheel, they touch the latter teeth along the whole tooth. 7. A toothed gear-wheel having teeth the top surfaces of which are ridge-shaped-in the longitudinal direction of the tooth in such manner that the height of the tooth, and, thus, the bending moment is decreased toward the ends of the tooth, said teeth being shaped in such manner that, when meshing with the teeth of anotherv gear wheel, they touch the latter teeth along the whole length of the tooth.

8. A toothed gear-wheel having teeth the top surfaces of whichare varied in the ,longitudinal direction of the tooth in such manner that the height of the tooth, and, thus, the bending moment is decreased toward the ends of the tooth, said teeth'being shaped in such manner that, when meshing with the length of the teeth of another gear wheel,"they touch the latter teeth along the'whole length of the 

